1. Field of the Invention
The invention relates generally to electrical apparatus and, more particularly, to enclosed switchboards having an integral lifting mechanism.
2. Description of the Prior Art
Switchboards are widely used in the distribution of electrical power from incoming utility company feeder lines to electrical loads distributed throughout a building or other facility. A plurality of circuit breakers are removably mounted one above the other within cells in the switchboard. Since circuit breakers are large and heavy, weighing up to 500 pounds, means must be provided to lift the circuit breakers to the proper height for insertion into their respective cells. For switchboards to be situated inside a building, forklift trucks, cranes, or other lifting apparatus may be used. However, switchboards to be located outdoors must be enclosed in a weatherproof housing, making it difficult or impossible to use conventional outboard lifting equipment to properly position the circuit breakers in their cells.
In the past, enclosed switchboards have employed special lifting mechanisms removably mounted upon the exterior of the housing or mounted within the housing on top of the switchboard. Prior art lifting mechanisms mounted on the outside of the enclosure would be exposed to weather if left in place continuously. Therefore, it was necessary to provide storage space for the lifting mechanisms and means to lift and mount the mechanism into proper position when it was desired to use it. This was often inconvenient and impractical.
Since electrical switchboards are constructed at a standard height of 90 inches, lifting mechanisms mounted on top of the switchboard within the enclosure required the enclosure to be larger than normal in order to provide proper clearance for the lifting mechanism between the top of the switchboard and the ceiling of the enclosure. Shipment of some prior art enclosed switchboards thus required a special low-boy truck for motor freight delivery. This resulted in an additional transportation charge ranging as high as several thousand dollars on long distance motor freight shipments.
It is therefore desirable to provide an enclosed electrical switchboard having a compact lightweight lifting mechanism which can remain permanently in its operating position within the enclosure while minimizing the total height of the enclosure to permit shipment on standard flatbed trucks.